Lighting devices are available on the market which are implemented as flexible linear modules.
Such devices are also available in a “protected” version, wherein a flexible light radiation source assembly is embedded into a flexible case, adapted to be made e.g. of polymer materials. The case is adapted to protect the light radiation source assembly (light engine) from the outer environment, without significantly affecting the performance thereof as regards light output performance.
In such devices, the individual light radiation sources (e.g. LEDs) are visible in the near field, i.e. when they are observed from a short distance. This event is considered negative, because it reduces the pleasantness and comfort perceived while observing light radiation.
At an indirect observation, the light radiation emission appears as irregular, with a higher luminance at LED positions and darker areas between them. This effect is considered unpleasant, for example in wall washing and cove lighting applications, wherein the light engine is arranged near the reflecting/diffusive wall surface.
The need is increasingly felt on the market to create protected modules adapted to provide a diffused lighting. In order to achieve this result, the case may be so structured as to be adapted to perform a luminance homogenization on the outer surface of the device, through a mixing of the light radiations emitted by the single sources. In this way it is possible to make the locations of LEDs less perceivable also at a short distance.
In various implementations, such a lighting device or module may be implemented so as to be able to bend up-down (or front-back): for example, it is possible to arrange the light radiation sources on a support board (for example a Printed Circuit Board or PCB) arranged horizontally within the case, the light radiation being emitted vertically.
Devices of this kind may be implemented, for example, by laminating the support board (e.g. the PCB) onto an extruded profile. Such a profile may be made of a diffusive polymer material, adapted to scatter light and provide the desired diffused appearance in near field.
The lamination may be carried out with a transparent glue, the position of the light radiation source assembly with respect to the extruded profile being determined by the amount of adhesive material, or through a conveyor supporting the components being carried in the production line.
By adopting the first solution, possible variations of the amount of glue may modify the distance of the support board from the profile. The second solution requires a rather close monitoring of the production line.
In order to avoid light spillage from the sides of the device, opaque side walls may be used which can be designed as inserts, which are extruded together with the central portion of the extruded profile. A possible change in the light radiation source assembly, for example deriving from a substitution of components (LED light radiation sources, drivers, etc.) may cause a variation of the available volume for the laminating glue and ultimately affect the final result.
Another possible solution is exemplified in DE 1020 12214484 A1.